Spherical dielectric lenses, also known as Luneberg lenses, have been widely used for antenna systems. A Luneberg lens is a spherical lens in which the dielectric constant varies as a function of the radius of the lens. The spherical lens shape has no intrinsic optical axis. Therefore, when a plane wave is incident on the Luneberg lens, the wave encounters an effective optical axis in the direction of the plane wave. The energy of the plane wave is then focused at a single focal point on the opposite side of the lens. This allows the lens to operate on multiple plane waves that are incident from different directions with little or no interference. Accordingly, the spherical lens is ideally suited for use in a multi-beam antenna system.
Conventional multi-beam antenna systems, which utilize a spherical lens, use a feed assembly that consists of a horn cluster and a switch tree made up of a number of switching circulators. Unfortunately, these conventional feed assemblies have several drawbacks. First, the conventional feed assemblies require a large number of active switching devices, which increases the complexity and the cost of the antenna system. Secondly, because the feed assemblies use horn clusters, the antennas can only provide hemispherical coverage due to blockage by the horn cluster. Finally, because the horn cluster fixes the beam pattern on a grid, these antennas experience losses due to scalloping.
Therefore, there is a continuing need for an inexpensive and low cost antenna feed for a beam scanning for a spherical dielectric lens antenna. In particular, there is a need for an inexpensive and low-loss antenna feed for a multi-beam RF spherical dielectric lens antenna that can provide spherical coverage.